choosing a vehicle for DMD

Hi,

My son is 9 years old with DMD and we are looking at purchasing our first wheelchair adapted vehicle. He has got too heavy to be lifting in and out of the car and it will be much easier if he can travel in his wheelchair. We have been told we will have to keep this motability car for 5 years. We have asked for financial help with the car from motobility grants and they have asked what our needs are, including what equipment our son needs, as this will detemine what size of vehicle they think we need. we have explained that DMD is progressive, so what he needs now might differ to what he needs in 4-5 years. He is getting measured for his powered wheelchair this week, anyone got any suggestions about what other equipment he might need within the next few years, up to age 14? thanks